title: AKAP350 Is involved in the development of apical "canalicular" structures in hepatic cells HepG2.
abstract: Hepatocytes are epithelial cells whose apical poles constitute the bile canaliculi. The establishment and maintenance of canalicular poles is a finely regulated process that dictates the efficiency of primary bile secretion. Protein kinase A (PKA) modulates this process at different levels. AKAP350 is an A-kinase anchoring protein that scaffolds protein complexes involved in modulating the dynamic structures of the Golgi apparatus and microtubule cytoskeleton, facilitating microtubule nucleation at this organelle. In this study, we evaluated whether AKAP350 is involved in the development of bile canaliculi-like structures in hepatocyte derived HepG2 cells. We found that AKAP350 recruits PKA to the centrosomes and Golgi apparatus in HepG2 cells. De-localization of AKAP350 from these organelles led to reduced apical cell polarization. A decrease in AKAP350 expression inhibited the formation of canalicular structures and impaired F-actin organization at canalicular poles. Furthermore, loss of AKAP350 expression led to diminished polarized expression of the p-glycoprotein (MDR1/ABCB1) at the apical "canalicular" membrane. AKAP350 knock down effects on canalicular structures formation and actin organization could be mimicked by inhibition of Golgi microtubule nucleation by depletion of CLIP associated proteins (CLASPs). Our data reveal that AKAP350 participates in mechanisms which determine the development of canalicular structures as well as accurate canalicular expression of distinct proteins and actin organization, and provide evidence on the involvement of Golgi microtubule nucleation in hepatocyte apical polarization.
authors.affiliation: Instituto de Fisiología Experimental, Consejo de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.
authors.forename: Stella M
authors.initials: SM
authors.lastname: Mattaloni
authors.forename: Elena
authors.initials: E
authors.lastname: Kolobova
authors.forename: Cristián
authors.initials: C
authors.lastname: Favre
authors.forename: Raúl A
authors.initials: RA
authors.lastname: Marinelli
authors.forename: James R
authors.initials: JR
authors.lastname: Goldenring
authors.forename: Maria C
authors.initials: MC
authors.lastname: Larocca
mesh_terms: D054758:A Kinase Anchor Proteins / Q000378:metabolism*; D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D001648:Bile Canaliculi / Q000378:metabolism* / Q000648:ultrastructure*; D016764:Cell Polarity / Q000502:physiology*; D018385:Centrosome / Q000378:metabolism / Q000648:ultrastructure; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000378:metabolism* / Q000648:ultrastructure*; D006801:Humans; D015151:Immunoblotting; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence
chemical_list: D054758:A Kinase Anchor Proteins; C119719:AKAP9 protein, human; D003598:Cytoskeletal Proteins; D017868:Cyclic AMP-Dependent Protein Kinases